110 
the great keel which springs from each branch internally. No cells are carried by the 
areas formed by the anastomosis of contiguous branches. ' 
I have only seen a single, very large and well preserved example of this genus, and 
a careful examination of this has still left me entirely unable to elucidate and explain some 
of the most extraordinary structural featuresw hich it presents. There can, however, be no 
doubt as to the complete distinctness of the genus from any previously known. A compre- 
hension of the very remarkable characters presented by this genus will perhaps be best ob- 
tained from a detailed account of the different figures of the above illustration, all of which 
represent different portions of the only known specimen. 
a. This figure exhibits a portion of the exterior of the frond, showing the fenestrules and 
the outer non-celluliferous aspect of the branches. In the portion here illustrated of the na- 
tural size, and partially shown at ) on an enlarged scale, the fenestrules are oval, and arranged 
in diagonal lines, and the branches are strongly keeled; the general appearance closely resem- 
bling the non-celluliferous aspect of Reteporu prisca (Goldfuss), and the fenestrules being 
- formed in the same way by the simple inosculation of the branches, without the development 
of distinct dissepiments. c. This represents another portion of the exterior of the frond, 
near the base, where the fenestrules are polygonal and are not arranged in regular diagonal 
lines. In some eases, the fenestrules present the appearance of being closed by a delicate ex- 
ternal membrane. 
d. This figure shows a small portion from which the outer non-celluliferous layer of the 
branches has been stripped off, showing the proximal ends or bases of the cells, arranged in a 
double inosculating row on each branch, and lying in the same plane as the fenestrules. 
e. This figure exhibits, on an enlarged scale, a small portion of the exterior of the frond 
from which the outer non-celluliferous layer and the cells themselves have been stripped away, 
leaving to view the circular mouths of the cells arranged in two alternating rows, which are 
still in the same plane as the fenestrules, and which do not encroach upon the spaces formed 
by the inosculation of the branches. 
f. This figure is a greatly magnified representation of a transverse section of the frond at 
a point considerably removed from the base, showing the branches cut across. Above, the 
branches are separated by the fenestrules, and immediately beneath this are seen the dark 
oval spaces contained within the body of each branch, a pair in each, and representing the 
cavities of the biserial cells. Below this, again, each branch is seen to give origin to an im- 
mense vertical keel or ridge, which is directed inwards towards the interior of the frond. 
These ridges are separated by deep intervening grooves ; and there can be doubt that the cells 
open at the bottom of these groves, those of one side of the branch opening on one side of the 
base of the great keel, and those of the other opening upon the opposite side of the same. 
g. This exhibits a greatly magnified transverse section of the frond at a point a little 
above the base. As in the preceding, we can recognise without difficulty the shallow fenes- 
trules, the divided branches carrying in their interior, each, a pair of cells, and the great inter- 
nal keels. Here, however, we have two new features, Firstly, the deep grooves between the 
keels are sub-divided by delicate calcareous laminze which connect the opposite side of contigu- 
ous keels, and divide the intervening grooves into shallow transverse chambers. Secondly, the 
grooves between the keels are closed internally by a continuous calcareous membrane, which 
has a minutely porous or vesicular structure. 
h. This exhibits a fragment taken from near the base, and showing the internal surface. 
We see here the inner faces of the great longitudinal keels, separated by shallow grooves which 
are filled up by a continuous calcareous membrane, which is not penetrated by either the 
fenestrules or the cells. No apertures, therefore, of any kind appear on the interior of the 
frond near the base. In the upper portion of the frond, however, a fragment of the interior 
exhibits simply the great keels with deep intervening grooves, and the layer connecting the 
keels cannot be distinctly made out. At the right hand corner of h, the keels and their con- 
necting membrane are broken away, and we see the cavities of the rows of cells; whilst the 
extreme corner is still further broken away, so that the fenestrules comes into view. 
i. This simply represents a singlé branch in transverse section, greatly enlarged, and 
shows the cells in the interior of the branch, and the great triangular keel proceeding from its 
internal surface. 
From the above description, it will be evident that the structure of Carinopora is quite 
anomolous, and wholly unlike anything that has been hitherto observed in any member of the 
